During the early-2260s, Pavel was romantically involved with Irina Galliulin, while they both attended the Academy together. The two had several disagreements before they parted ways: Pavel believed Irina to always be too free-spirited, Irina believed Pavel to have always been rigid. When Irina dropped out of the Academy, each accused the one of leaving the other. Pavel left, but came back to look for Irina, who was at the time staying in the city with friends. Irina would eventually join the counterculture movement of Dr. Sevrin, and his search for the mythical planet Eden. (TOS: "The Way to Eden")

Chekov would have likely been assigned to the Enterprise after the events of "Mudd's Women", as Chekov did not know Harry Mudd when the crew encountered him a second time in "I, Mudd". Chekov's first dated appearance on the Enterprise is on stardate 3018.2 in the episode "Catspaw". Although the character of Chekov had not yet joined the cast during the first season, he must have been assigned in some capacity by 3141.9, and an off-screen encounter with Khan must have occurred during his assault in "Space Seed"; Khan recognized him over fifteen years later on Ceti Alpha V, stating "I never forget a face..." (Star Trek II: The Wrath of Khan). Koenig jokes that he believes Chekov accidentally made Khan wait an uncomfortable amount of time to use the bathroom.

On a mission to deliver supplies to a Federation experimental colony on the planetGamma Hydra IV, the six member landing party discovered that most of the colonist were either dead or close to death from rapid aging with Chekov becoming frightened upon finding a dead body in one of the buildings. On return to the Enterprise the entire landing party was infected with the rapid aging except for Chekov. Chekov complained to Sulu about how many times Dr. McCoy put him through a series of test to discover why he wasn't aging, especially emphasising that if he gave any more blood he wouldn't have any more. Spock soon discovered that the rapid aging was caused by radiation left on Gamma Hydra IV from a rogue comet. McCoy determined that the cure was adrenaline. Chekov had been so shocked upon finding the dead body that his adrenaline provided an immunity to the radiation's effects. (TOS: "The Deadly Years")

In 2268, Chekov, Kirk and Lieutenant Uhura were captured by alien beings who used them in gladiatorial combat, which the beings wagered on. Such captured beings were known as "thralls". One of the thralls, Tamoon was assigned to train Chekov in gladiatorial combat and developed romantic feelings towards him, leading to many unwelcome advances. (TOS: "The Gamesters of Triskelion")

Chekov was killed as a member of the landing party that made contact with the xenophobicMelkotians. The Melkotians considered humans as a disease that must be destroyed, and placed the five member landing party in a frontier setting during the time of Wyatt Earp. The away team filled the role of the Clantons, one of the two major gangs involved at the OK Corral gunfight with Chekov playing gang member Billy Claiborne. Chekov was killed by one of the Earps over a girl named Sylvia, who was in love with him, and not the Earp that wanted her. Spock realized that this simulation was not real, and thus the four other landing party members could not be hurt as long as they did not believe in the illusion. After successfully escaping the illusory Wild West setting, the landing party was transported back to the Enterprise, along with Chekov who was alive once again and the Melkotians were willing to begin talks to join the Federation. (TOS: "Spectre of the Gun")

When the ship was hijacked by androidNorman to an undiscovered planet, the Enterprise's crew discovered Harcourt Fenton Mudd who had crashed on the planet. The planet was populated by androids who wished to use the Enterprise to visit other planets, but strand the crew there. The androids tempted Chekov with a planet full of beautiful women to serve him. In the end, the crew banded together and escaped the planet, leaving Mudd with 500 android replicas of his overbearing wife, Stella. (TOS: "I, Mudd")

Chekov was at navigation when he noticed the Enterprise navigation controls were not working, and then tried to assist Lieutenant Hadley, manning the helm, with the helm's stuck controls. That's when the KelvanHanar suddenly transported himself onto the bridge and put Chekov and the rest of the bridge crew into temporary 'frozen' and motionless stasis. Two other Kelvans, Tomar and Drea, had already seized control of Engineering and environmental engineering in a similar fashion. Thus began the attempted hijacking of the Enterprise by the Kelvan Milky Way Expedition so they could return to the Andromeda Galaxy. After the Enterprise successfully exited the Milky Way galaxy through the Galactic barrier, Kelvan leader Rojan neutralized and reduced Chekov into a dehydrated porous cuboctahedron solid, the size of a human fist, composed of Chekov's base minerals which represented the "distilled" essence of Chekov's being, because he was considered along with most of the rest of the crew non-essential personnel. Chekov was reconstituted after Kirk, Spock, McCoy and Scotty, the only four of the crew who were not neutralized, regained control of the Enterprise. (TOS: "By Any Other Name")

After the Starnes Exploration Party children were brought aboard the Enterprise from the planet Triacus, no one on board knew that the children were under the influence of Gorgan, who had given the children the ability of mind-control. This telekinesis had already caused the deaths of the children's parents and was the way in which Gorgan hoped to achieve galactic dominance by way of other children. The children used their mind-control on Chekov, Sulu and Uhura to make them believe that the Enterprise was still orbiting Triacus, when in actuality Chekov and Sulu had set course for Marcus XII, the intended next target for Gorgan. This also caused Kirk, unaware of the change of course and the departure from the orbit of Triacus, to have two redshirts have their molecules beamed into and spread throughout space and to their deaths. Then Tommy Starnes manipulated, by telekinesis, Chekov, Security Chief Freeman and another Security Guard Redshirt attempted to arrest and put in the brig both Kirk and Spock because of false "orders" of Starfleet command. Kirk and Spock fought off Chekov, Freeman and the other Security Guard who were temporarily put in the brig themselves. Chekov was freed from the mind-control once the children were freed from the influence of Gorgan. (TOS: "And the Children Shall Lead")

Chekov was rendered unconscious by the EymorgKara when she boarded the Enterprise and used her control bracelet in order to steal Spock's brain. After the crew regained consciousness and found Spock's body without his brain and they found Kara's ship left an ion trail to the Sigma Draconis system, Chekov placed a schematic of the system on the bridge's viewscreen. A debate ensued between Chekov, Sulu and Uhura as to which of the three Class M planets they should look for Spock's brain, with Kirk reminding them that Dr. McCoy said that Spock would have only three hours to live without his brain. None of the three planets seemed capable of supporting interstellar flight, but Kirk's best hunch of where to look came from Uhura, who found large, regular energy pulsations on the otherwise glaciated and pre-industrial Sigma Draconis VI. Chekov was part of a landing party that also consisted of Kirk, Scotty, McCoy and two redshirts who beamed down to the surface of Sigma Draconis VI. There the landing party suffered an ambush by the Morg, primitive humanoid men until one of them was subdued by a phaser. The Morg that was hit hinted at "the Others" who gave "pain and delight", but seemingly the Morg had no mates and didn't know what a female was. Chekov then ran his tricorder and found evidence of an underground city. As Kirk, McCoy, and Scotty went underground and found that the Eymorg were the females of the Morg, and then discovered Spock's brain was being used to power the city, Chekov used his phaser to heat a rock to keep him and the two redshirts warm. McCoy was able to get Spock's brain back in his head, just in the nick of time, and they met back up with Chekov and the two redshirts leaving the Eymorg to have to start living with the Morg. (TOS: "Spock's Brain")

When Spock mind-melded with MedusanAmbassadorKollos to guide the Enterprise into normal space from being stranded in an uncharted void of the galaxy, by a then dead Larry Marvick, Spock-Kollos took over, temporarily, the helm console from Sulu and was assisted in the task by Chekov at navigation. Unfortunately Spock-Kollos forgot to put back on the visor, which caused Spock to go temporarily insane while still on the bridge. In this temporary insanity, he pushed very hard backwards both Chekov and Sulu, who were trying to help him, with Chekov landing on top of the navigation console and then to on his back on the floor. Fortunately Chekov recovered quickly and Spock would do so, as well, a short time after that. (TOS: "Is There in Truth No Beauty?"))

Chekov was part of an away team that beamed aboard the starship USS Defiant, which was adrift in space. They discovered that the ship was dissolving due to the effects of the interphase of that part of space . They also discovered that there had been mass insanity aboard the USS Defiant with its whole crew dead. Kirk unfortunately had to remain behind because the transporter could only beam aboard three of the four away team members. After beaming back to the Enterprise, Chekov attacked Spock in a fit of madness. The illness then spread throughout the ship. The interphase was now causing mental breakdowns in the crew of the Enterprise. Chekov was cured of his madness the same way the rest of the crew who suffered mental breakdowns did, from Dr. McCoy discovering and then dispensing a diluted theragen derivative. Spock would tell Chekov that it was great to see Chekov back to his normal self. The crew rescued Kirk and escaped the Tholians. (TOS: "The Tholian Web")

Near the end of 2268, Chekov was very nervous when Kirk, Spock and Scotty were forced to activate the three-part self-destruct sequence in order to force CommissionerBele to relinquish control of the Enterprise to Kirk. Shortly after in the recreation room, Chekov attended the speech by Lokai regarding how his people had been enslaved and then subjugated by Bele's people on their home planet of Cheron for many centuries. Chekov expressed surprise about this by saying to Lokai, "There was persecution on Earth once. I remember reading about it in history class." Sulu then reminded Chekov that that took place several centuries earlier on Earth and was considered primitive thinking in the 23rd century. Chekov, manning the bridge's main science station for Spock, would later be the one to discover that Bele sabotaged the self-destruct porgram so he and Lokai would end up having their final battle on the already mutually annihilated, by civil war, Cheron. (TOS: "Let That Be Your Last Battlefield")

Early in 2269, Chekov's sight would be affected when the "lights of Zetar" beings attacked the Enterprise as the ship was trying to reach Memory Alpha. Apparently as navigator, Chekov's sight was considered by the Zetarians to be the most important part of Chekov's brain to render useless in the young man during the attack. Chekov later expressed that he couldn't force himself to look at the navigation controls during the attack. (TOS: "The Lights of Zetar")

A bit later in 2269, Chekov once again encountered his lost love, Irina. Although they were initially happy to see one another, Chekov adamantly disapproved of her new lifestyle and attempted to cast her off. She visited Chekov, who was working in Auxiliary Control assigned to help Spock locate the planet Eden, to apologize for upsetting Pavel. Her ulterior motive, however, was to subtly use him to gain his knowledge of the systems of the ship, which were later used by Dr. Sevrin and his followers to hijack the Enterprise. The two left each other once again, this time while saying "good-bye" to one another, as well as each with a better understanding of the other. (TOS: "The Way to Eden")

Chekov and Sulu refusing to comply with the Captain's orders as Kirk's body was inhabited by Dr. Janice Lester in 2269.

A short time after that unaware that Kirk's body was being inhabited by Dr. Janice Lester after a life-energy transfer, Chekov and Sulu started protesting when the Captain extended the mutiny charges against Spock and the doctor to Scotty and McCoy and ordered the death penalty for all four of them. Chekov persisted and tried to remind the Captain that the death penalty was forbidden except for violation of General Order 4, which had not been violated. But the Captain refused to listen. A short time later on the bridge, Chekov and Sulu took their hands off their consoles in defiance of the Captain's orders to go to the planet Benecia for the internment of the prisoners. This action by Chekov and Sulu fortunately started the process of returning Kirk back to his own body. (TOS: "Turnabout Intruder")

By putting Ceti eels inside their heads, Khan made them susceptible to his suggestions, his motive being to seek revenge on Admiral Kirk. Using Chekov and Terrell, Khan was able to seize the Reliant and subsequently steal the Genesis Device.

The Enterprise was disabled by a Klingon Bird-of-Prey in orbit around the Genesis Planet and was then self-destructed by Kirk (with help from Scotty and Chekov) to prevent its capture. Kirk and his crew later seized command of the Klingon ship, which they named the HMS Bounty.

Using the slingshot effect, the Bounty went back in time to 1986, to transport two Humpback whales to the 23rd century. While on Earth, Chekov and Uhura were part of "Team 2," assigned to locating and acquiring photons for recrystallizing the dilithium crystals aboard the Bounty.

Although the mission was a success in acquiring the necessary photons from the nuclear vessel, USS Enterprise, Chekov was captured by the ship's security. Accused of being a "Russkie," Chekov made a failed escape attempt from the aircraft carrier, only to become critically injured when he fell over fifty feet from the ship's hangar deck, running through an open hatch that led out to one of the ship's massive aircraft elevators.

In 2287, Chekov took command of the Enterprise-A and posed as "Captain Chekov" as a ruse to negotiate with Sybok for the hostages that the renegade Vulcan took on Nimbus III, while Kirk, Spock, Uhura, and a security team landed on the planet covertly by shuttlecraft. Chekov successfully distracted Sybok long enough for the landing party to launch an attack on Paradise City. (Star Trek V: The Final Frontier)

Chekov, shortly before the Enterprise-A's decommissioning

In 2293, Chekov undertook his final voyage on the Enterprise-A as part of the mission to escort the Klingon Chancellor to peace negotiations with the Federation. Chekov used his investigative science background to find forensic evidence linked to a Federation-Klingon conspiracy attempting to undermine the peace talks. After the Khitomer Conference, Chekov's last duty on the Enterprise-A was to man navigation and the helm for her decommissioning cruise. (Star Trek VI: The Undiscovered Country)

Pavel was very proud of his heritage. He often noted (sometimes erroneously) that most great inventions and events ever noted in history came from his homeland, which both amused and annoyed his crewmates:

He claimed that the old Earth saying: "Fool me once, shame on you. Fool me twice, shame on me," was invented in Russia. (TOS: "Friday's Child")

He claimed that the Garden of Eden was located just outside Moscow. He claimed that it was "a very nice place" and that "it must've made Adam and Eve very sad to leave." Which Kirk sarcastically responded with "Just..outside Moscow, all right" (TOS: "The Apple")

In addition to these, Captain Kirk once stopped Lieutenant Sulu mid-sentence, while Sulu was referencing an incident in Siberia, and told Sulu, "If I wanted a Russian history lesson, I would have brought Mr. Chekov." (TOS: "That Which Survives", in which Chekov himself did not appear)

In the novel Prime Directive, Chekov claimed that karate was invented in Russia before being stolen by the Chinese.

In the video game Star Trek: Judgment Rites, Chekov claims that cognac was a Russian invention.

Chekov was played by Walter Koenig, who joined the cast of Star Trek at the beginning of TOS Season 2, and filled in what were originally intended to be roles for Hikaru Sulu while George Takei spent much of this time involved in filming The Green Berets during Season 2. ("To Boldly Go...": Season 2, TOS Season 2 DVD special features)

According to Gene L. Coon in his The Making of Star Trek, Gene Roddenberry wanted to add in a young, Englishman to appeal to younger demographics. However, he received a written complaint from Russian sources, who complained that Star Trek–though trying to fashion a future where the world was united–was ignoring the USSR, which, at the time, was the leader in the Space Race. Roddenberry soon after altered his English youth into Pavel.

On the video release of "William Shatner's Star Trek Memories," Walter Koenig himself said that the Russians didn't say anything about there being no Russians on Enterprise and the Pravda article that Roddenberry and Coon referred to likely didn't exist because at the height of the Cold War, no American programming was airing in Russia. (Allan Asherman's The Star Trek Compendium says that the Pravda journalist "[had] seen a Star Trek episode televised in Germany", but Star Trek didn't air in Germany until 1972.) According to Koenig, the character was added to add Davy Jones-like appeal to the show and that the Russian heritage was added by Roddenberry indeed because he wanted to honor the fact that the Russians were the first people in space. In his first couple of episodes, Koenig indeed wore a Monkees style wig to look more like Davy Jones. ("To Boldly Go...": Season 2, TOS Season 2 DVD special features) (Ironically, during the time of TOS in the late 1960s, Soviet teens sporting this look, derisively called "haries" and viewed as dangerously rebellious by their elders, were often arrested and had their hair cut off by the police.) [1]

In Star Trek Generations, Chekov was briefly referred to as "Captain Chekov" by one of the reporters on the Enterprise-B. Chekov was referred to in the script as "Commander," and was still wearing a Commander's pin.

An episode was developed for the seventh season of Star Trek: The Next Generation that would have featured at 24th-Century Pavel Chekov. Writer Naren Shankar is quoted in the September 1994 issue of Sci Fi Universe: "It never went anywhere. I was working on a Chekov story where he returns as a prisoner-of-war from a planet where he was imprisoned for many years and finally released. Now he has come back as an ambassador to help the Federation open up diplomatic relations, like Vietnam, essentially. The story was going to be about Worf and Chekov, because they're both Russian and Worf has heard about him and they kind of strike up a relationship together. Throughout the course of the negotiations with these people, it appears as though Chekov is sabotaging them. It turns out he is plotting to use the Enterprise to lay waste to their capital for revenge and to screw things up for the Federation because he feels they abandoned him and let these people torture him."

One of his costumes was added to the ScienceFictionArchives.com collection and was showcased at Paris science museum during 2010-2011 exhibition "Science (and) Fiction: Imagination Meets Reality".[2]

In the Star Trek: Starfleet Academy game, Chekov claims he was stationed on planet Benderi IV prior to joining the Enterprise where he had a commanding officer who believed getting angry was unprofessional and bottled up her rage until it exploded. He also authored several simulator missions used at the academy.

In the novel To Reign in Hell: The Exile of Khan Noonien Singh, Chekov led the security team that delivered Khan and his followers to Ceti Alpha V's surface. Khan remembers Chekov as having led a courageous but failed attempt to retake the engine room during Khan's brief takeover of the Enterprise. This coincides with both Khan's recognition of Chekov, as well as Chekov's comment in the novelization for Star Trek II: The Wrath of Khan that he had seen the world Khan had been left on.